Guiding grids of the above-mentioned kind have become known by a multitude of documents, such as U.S. Pat. Nos. 4,179,247 or 5,146,752. U.S. Pat. No. 5,146,752, in particular, illustrates how laborious it is to mount the individual parts of the guiding grid in the housing, since various parts have to be matched, patched and fitted with one another and have to be interconnected, particularly when inserting them into a turbine unit or a turbocharger. It is clear, that such a construction is expensive.